Electronic apparatus comprising an input stage with a binary output connected to a relay control circuit

摘要

An electronic apparatus has an input stage (11) with a binary signal output (19). This signal output is connected to a relay control circuit which deenergizes or energizes the relay (15) in dependence on the output signal (0 or 1). The relay (15) can be held in the energized condition over a wide voltage range, without being overloaded, by a periodically limited energizing current. This is achieved, by way of example, by energizing the relay via a semiconductor switching device (transistor 14) which can be switched on and off by a Schmitt trigger (12) connected to the binary signal output. A capacitor (17) charged in dependence on the energizing current flowing through the relay is used to override the signal from the binary output (19) to switch the transistor (14) via the Schmitt trigger (12) so as to periodically energize the relay (15) (FIG. 1).